I made these a while ago on our company's 3D printer, and I figured I'd upload the pic for anyone who's curious. I made them with a compound angle, meaning that the highest corners are where the F2 and F8 keys are, and the lowest corners are the Popup and Pause Break keys. Those actually touch the desktop, which is why the holder is split like it is.

For the very curious, the little dark spots you see on the top surface is just where the plastic from the 3D printer didn't cover completely. I must have used too thin of a wall on the top surface, but it doesn't matter, since the keyboard sits flat on the whole surface. The circle in the center is just for design, I could have just as easily made it an X shape. The little "legs" standing up around the edges hold the keyboard halves firmly in place.

Those look very nice indeed! I'm guessing you have some kind on non-slip sticker underneath them, right?

Could you export that 3D shape into a standard format and upload it here so that others can benefit from it? I have zero experience with 3D printers but I imagine there must be something analogous to XML or PDF in the 3D-printing world that would be useful.

No, I don't use any non-slip underneath. The pads don't really move around on my desk during normal use, and I do slide them from time to time on purpose to adjust them as I shift my posture throughout the day.

There is a type of file that others could use. It is a .stl file, which is typically used by any 3D printer software. I've attached the Left and Right hand files in the zip file.